Report nav timing 2 instance as soon as it's requested.

third_party/WebKit/Source/core/timing/PerformanceEntry.h

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  * Copyright (C) 2012 Intel Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 53 matching lines @@
     Render = 1 << 4,
     Resource = 1 << 5,
     LongTask = 1 << 6,
     TaskAttribution = 1 << 7,
     Paint = 1 << 8
   };
 
   String name() const;
   String entryType() const;
   DOMHighResTimeStamp startTime() const;
-  DOMHighResTimeStamp duration() const;
+  // PerformanceNavigationTiming will override this due to
+  // the nature of reporting it early, which means not having a
+  // finish time available at construction time.
+  // Other classes must NOT override this.
+  virtual DOMHighResTimeStamp duration() const;
 
   ScriptValue toJSONForBinding(ScriptState*) const;
 
   PerformanceEntryType entryTypeEnum() const { return m_entryTypeEnum; }
 
   bool isResource() const { return m_entryTypeEnum == Resource; }
   bool isRender() const { return m_entryTypeEnum == Render; }
   bool isComposite() const { return m_entryTypeEnum == Composite; }
   bool isMark() const { return m_entryTypeEnum == Mark; }
   bool isMeasure() const { return m_entryTypeEnum == Measure; }
@@ skipping 18 matching lines @@
   const String m_name;
   const String m_entryType;
   const double m_startTime;
   const double m_duration;
   const PerformanceEntryType m_entryTypeEnum;
 };
 
 }  // namespace blink
 
 #endif  // PerformanceEntry_h